Stroke Theory

Mar 8, 2014 |

What follows is a discussion of my ideas about stroke dynamics. It’s an evolving science with abundant subjective input and assertions ruling the day. My ideas come from studying what makes powerful strokes and what it takes to paddle hard all day- in essence- what it is to work hard with a paddle. A lot- perhaps most- of my ideas fly in the face of modern paradigms.

To put it into context I think it helps to understand how the modern paradigms have come about. But- be forewarned – a lot of this stuff you’ve never heard of or been taught in kayak school. So there’s a good chance a lot of it is plain wrong. I present it only as knowledge of what I know works for me and my needs.

To understand why paddles are the shape they are now, it helps to look at where they came from and where they’re going. The bulk of stroke science has come from the racing community. Flatwater racers film themselves in slow motion and carefully study every inch of their strokes and form in an effort to optimize their workload and its efficiency. A 5% improvement for them would be huge. They are concerned with accomplishing the highest possible workload in a given time- and getting maximum speed for that workload.

Slalom and wildwater racers learn from the flatwater racers what ideal ergonomics can be and mean. This is meaningful, result verified science being carefully and ponderously put down over decades towards this one ideal- a perfect work dynamo. Forward results per effort is the golden fleece here. But I don’t think it’s EVERYONE’S golden fleece. The jist of the present racer-driven technology is to get as much efficient work as possible done in a given time. This intent has driven design since the first curved powerface blade shapes hit the scene in the 60’s- an artifact of early European touring customers and slalom racers.

Â Ancient inuits used to participate in life-or-death kayak warfare. Paddle hard and long- or die! And they never resorted to curved powerfaces. Non-the-less, present stroke and blade shape theory comes from a long history of racers trying to optimize their efforts.

For instance, one of the things racers have learned is that the most fertile realm for increasing the work ability of each stroke is in the “catch” portion of the stroke. Most average paddlers could easily make their paddle strokes 5-10% “stronger” by getting a more solid catch- perhaps the softest portion of the stroke. Towards this end racers have used curved powerface paddles because they present a more aggressive catch angle for the blade. You increase the “pull” of the stroke in the vulnerable catch section this way.

Racers then disregard the compromised angle of the tip later in the stroke as the tip angle starts to undercut the true line of the workload. But the idea is to get an instant slam into gear, have the paddle hold tight, and then you pull the boat past the ‘frozen” paddle. This way, in theory, no eddy forms behind the paddle and you don’t spend precious energy to “stir” the water. Of course, in the real world the blade will pull a bit through the water, a tiny eddy will form, and you will spend a bit of precious energy to “stir” the water. Net result? The paddler is still loaded up on full torque- but some of the energy he is using is stirring water- not moving the boat forward. This tiny aspect- “the full catch”- has mercilessly driven stroke theory for decades.

Another effort to optimize the catch portion of the stroke is to bring sharp corners down to the entry point of the stroke. These corners generate nasty little eddies of course- but those are just extra drag in a system full of huge drag and this turbulence goes unnoticed except as a “wiggling” effect on the paddle. The problems with corners for average paddlers is that they wear much much faster and they slam the body with each stroke- all to optimize a portion of the stroke only 10% of the paddlers even know about.

Corners on the upper blade tip also quickly degenerate Duffek attempts by putting serious spin torque on the shaft as this little corner engages. Your Duffek will want to spin out of your hands- but only when you need it most.
Without going on and on trying to point out failings of the modern paradigm, I’d rather just attempt to say what I feels works for powerful strokes used all day long. The idea here is to accomplish a HUGE workload in the most body-friendly way. A lot of this has to do with eliminating the “slam” of the paddle in each stroke and also in reducing the torque generated from each stroke.

I feel the best time to do hard work on a stroke is when the ergonomics are best suited for it. That is, when the largest muscle groups are in their most powerful configurations. This is in the “power” section of the stroke- after the catch and before the withdrawal. The power section of the stroke is approx. 15%-90% of the way through the stroke and is when the most muscles can do the most work- easiest. This is the most important section of the stroke in my mind.

You want to adjust the torque and stroke rate of this section so that at most speeds the blade is barely catching and at higher torque rates the blade pulls through the water a bit. This ‘stirs” a lot more water but my feeling is- “Hey I don’t care what’s going on out there in the world- I want “X” amount of torque out of my stroke. If that torque is stirring water or pulling boat- I don’t care. My only concern is getting perfectly tweaked torque.”

Why the lack of concern about issues racers have labored over for decades? Because I feel the ultimate goal is to preserve and groom the body. You need this guarantee that your muscles won’t get overtorqued and get ‘slammed”. Racers need their muscles to get slammed on every stroke. They need to accelerate on stroke #1 and maintain high speed throughout. Most cruisers paddle hard to avoid obstacles or get out of trouble. And while this is an important time to optimize everything- “emergencies” are the exception and not the rule. Bottom line- most paddlers rarely if ever paddle as hard or efficiently as racers.

So- does the science really translate to these varied uses perfectly? I say no. Racer’s needs are different. They NEED abusive technology. They NEED to slam into third gear all day long. Let them slam away. I have a different agenda. The paradigm however is to follow the racer ethic and intent- in spite of the handicaps they bring.
So- without further adieu- I’d like to describe what I consider to be the dynamics of a good stroke. Stroke power comes from your abs and other core muscles. They are translating the work of the arms into language for the boat. This is an interesting aspect because flexing your abs also keeps you from breathing deeply. A lot of racer technology calls for “torso rotation”.

While it is impossible to erase this rotation I don’t agree with the idea of consciously twisting your torso. I think your body needs to accept the workload of the stroke the same way a tree accepts the workload of the wind. That is- the branches do the bulk of the work (and motion) but- as they get closer and closer to the center of the tree- there is less and less flexation. The abs hold relatively firm while turning just enough to set up the major muscle groups of the upper body. The abs anchor the stroke and you don’t want your anchor flagging in the breeze. I’ve been told this is a proper amount of “rotation” but I never consciously rotate my trunk. It leaves my abs too far extended to work on the next stroke.

If the abs are translating the work- I don’t want them to have too much free time. So I try to minimize the “airtime” of each stroke. The “airtime” is the period of time when both blades are in the air. Minimizing airtime leads to a staccato rhythm of the stroke- somewhat slower through the water section of the stroke and then quickly flashing through the air section. You achieve this by paying attention to the withdrawal of the previous stroke. You have to pull the blade forcefully out of the water edgewise. This is when the cross-sectional “wing” aspects of the blade come into play. A clean balanced wing rips effortlessly out of the water and speeds you on your way through the air section of the stroke.

This technique also speeds you through the catch of the next stroke- a sin to racing intent. The idea of a racing stroke is to do as much work as possible in the first third of the stroke. The idea here is to speed smoothly through this third to set up the power section of the stroke. Again- a key aspect to getting through the catch smoothly is how the paddle behaves edgewise as a wing. You want minimal flutter or drag. I think all paddles flutter somewhat. This is largely due to the eddy generated behind the blade- exacerbated by cornery tips. The acid test for a “no flutter” blade would be to be able to take a stroke with both hands completely open and to not have the blade fluttering at all under those conditions- pretty idealistic and unnecessary in my opinion. I just want the paddle to be “bland” and not “talk to me” at all. I want to boss it completely and not have to play the game on its terms.

Â “Power” or not- I don’t want the paddle talking back to me- ever. If you look at the trail of bubbles coming off the tip of most paddles- you will see trails coming off each corner of the tip (two trails). My round tipped paddle shapes have just one bubble stream coming off the tip. I think this is an indicator of the wing aspect drag- or lack thereof.

So- in my opinion the blade should slice quickly and smoothly through the catch of the stroke to set up optimal conditions for the power section. You want to be careful to not slam your muscles here.

Â A key issue with optimizing the power section of the stroke is to keep the blade as close to the boat as possible. This better aligns the line of work being done (the blade charc) with the line of resistance (the charc of the center of mass of the boat/rider). Ideally you would align the work line directly behind the load line- like a rocket. But this is impossible in a kayak so the next best thing it to try to keep the work charc as close as possible to the load charc. This means keeping the blade as close to the boat as possible. This is why I trim my blades in the throat section. It optimizes blade position for the power section of the stroke and also keeps the blades lighter and stronger and reduces how much they get dinged up by the boat.
I do still believe the old racer ethic that a strong stroke should be a little more push than pull. This is the best way to improve a stroke. Strokes which are mostly pull just look terrible and you can’t really get your back into them. But I have a tricky way of adding push with little added effort. It involves a subtle downpulling of the upper (pushing) hand. It requires a slight tensioning of the pec muscles in front of your shoulders and it lets you get your weight into the stroke a bit without raising your stroke rate much. So there is this slight but pervasive sense of coming down a bit with your upper hand. In fact the upper hand- starting close to the shoulder and punching forward in a slightly declining plane- only drops maybe 2″ vertically in the course of the stroke. But I’ve found this technique to add power with little deficit.

Another way I’ve found to add power to a stroke is by tensioning the rhomboids of the pulling arm. These are the muscles which attach the shoulder blades to the backbone . It’s easy for paddlers to let the rhomboids stretch out to let the shoulder blade fall into a stagnant “fallen forward” position where they anchor the armwork closer to the belly. If you remember to use your rhomboids- you are enhancing the anchorage of each stroke through your backbone and hips into the boat. It amps up the pull of your stroke with minimal added effort- and more importantly- it helps optimize the pull.

Another technique which helps sometimes is to use a version of the “wing stroke” flatwater racers use with their wing paddles. That is a stroke involving a progressive outward movement of the lower blade during the stroke. It starts in close to the boat -BUT- the outer (almost “upper”) edging becomes the leading edge of the wing and works outward- away from the boat during the stroke. This helps a lot in endurance situations because it opens your lungs at the end of the stroke another 10-15% I’d say than a standard straight back pull- which tends to pinch up the lungs on the pull side at the end of the pull. This opening of the lungs on the pulls side lets them have much better ventilation. What’s good about this stroke is that it still allows you to optimize the biggest and best muscle groups. There’s minimal sacrifice involved (you are having the work charc leave the load charc– thus setting up a turning momentum), but it does take concentration- so you can’t, and don’t need to, use this aspect all the time. I also like how it minimizes the airtime before the next stroke.

On my hardest strokes I use a kind of karate theory to maximize my push. I try to dense down the area of my hand that I am pushing the paddle with to the base of the first two fingers and keep good bone alignment with the workload. My hardest strokes have good bone alignment driving a tiny spot on the pushing hand so I am really amping up the psi of one spot- focused pressure. I’m not sure if that’s good science or not- I just like to do it. I think without good bone alignment- such as you find with lower feathers where you are pushing more with the palm section of the hand- means your tendons and ligaments are working harder to keep you hand from flopping back. It’s muscles keeping the pressures aligned- not bones. So for a nice endurance forward stroke your forward hand drops slightly to help your weight “climb on top of” your stroke- but your wrist doesn’t cross the centerline of the boat. My hand might just cross the centerline- but not the wrist.

A simple way I’ve found to get great alignment for the end of the stroke is to have the inner outline of the arm and paddle visually “close in” on the perimeter of the bow- in a symmetrical and parallel manner in the final moment of the stroke. It’s like your upper arm is “closing down” on the stroke and is clamping into a parallel alignment with the sides of the boat- with the wrist just hitting the center line. This is a much more “rockered” stroke than racers can use- they have to try to pull parallel to the water’s surface. The rocker of this stroke more closely parallels the rocker of the boat than the water’s surface. I think this helps the boat “climb the hill” of the bow wave in a very minor – but beneficial way. It’s a way of toying with the hull speed- without railing against it and I think lends itself to enhanced endurance. The strokes “feel easier” and I especially like them when I am tired at the end of the day. It’s no way to exceed your hull speed- like racers must on a consistent basis. I think it’s more along the lines of the “path of least resistance” and lends itself to a more fluid, body friendly stroke. The stroke ends virtually in front of your belly. There might be some withdrawal space used up behind your belly but all the pulling work needs to end by the front of the belly. At that point the upper arm has just finishing “closing down” on the last alignment of the descending push stroke.

So I guess the keynotes of a proper stroke by my definition are 1.) flexing evermore outward from relatively stable abs, upper arm “closing down” on the stroke with great alignment, minimal ‘airtime’, and the lower arm pulling outward slightly and making sure your rhomboids are working towards the end of the stroke. That’s a lot to look for in a common stroke but it’s what I find easy to do at the end of a long day and it’s an effortless way to maintain clean form even when you are very tired.

Stroke “no-no”s would be pulling more than pushing the stroke, or pulling too far, or twisting the lower torso too much, or too much airtime between strokes, or too hard a catch which slams muscles needlessly. Long lists each- but I thought I’d share them with you. Take them or leave them- it’s just my ideas- not some immutable laws or something.